This invention relates to fluid pumps and in particular to air pump assemblies.
This invention has particular application to air pump assemblies which may be used for light duty applications such as for supplying air to domestic spas and the like and particular reference will be made hereinafter to such applications. However this invention is not limited to such light duty applications and embodiments thereof may be used for supplying air to commercial spa baths or in industry for processing or supply applications where an air supply or suction effect is required.
The presently available light duty spa pump assemblies mostly utilize air pump/motor combinations which are mass produced for general use in vacuum cleaners. For this purpose such air pump/motor combinations include a pump mounted coaxially with and driven by an electric motor and will be hereinafter referred to as of the type described. These air pump/motor combinations mostly pass the compressed air from the pump through the motor for cooling purposes.
When such air pump/motor combinations are used for spas they often suffer premature failure. Frequently this is attributable to the motor overheating upon start-up during the period of little or no air circulation through the motor as the water is being purged from the air lines. In many installations these lines are relatively long. This is often exacerbated by accommodating the motor within a confined insulated housings in an effort to reduce the noise emitted from such motors which may spin a centrifugal pump impeller some 20,000 RPM.
Failure also occurs as a result of the contamination of the motor with chlorine or salt condensing from the spa water which fills the air supply lines upon shutdown. In conventional arrangements the return air from the pool is focussed on the motor and condenses on the steel housing and metal parts thereof. This corrodes the electrical components and causes or attributes to such failures.
The present invention aims to alleviate at least one of the abovementioned disadvantages and to provide air pump assemblies which will be reliable and efficient in use.
With the foregoing in view, this invention in one aspect resides broadly in an air pump assembly including: anair pump of the type described;
a partitioning wall through which the air pump extends with the motor at the opposite side thereof to the centrifugal pump;
an open pump housing closed by the wall;
an air inlet to the pump housing and associated confining means confining the air inlet to the pump inlet;
an open motor housing sealably engaged with the pump housing to form a sealed air pump housing assembly;
an air outlet from the air pump housing assembly, and
air communication means between the motor housing and the pump housing.
This arrangement has the advantage of simplicity of assembly in that the air pump may be mounted to the wall and then engaged with the pump housing so as to sealably engage the air inlet with the pump inlet. Thereafter the assembly may be completed by securing the motor housing to the pump housing. Preferably the housing parts are moulded complementary plastics components to facilitate manufacture and assembly.
The air outlet may be in the motor housing but preferably the air outlet is in the pump housing so that return air or water vapour is somewhat isolated from the motor housing. It is also preferred that the air outlet be formed at a lower part of the pump housing and that the air communication means be spaced above the air outlet.
In the case of a vertical pipe mount the air outlet is preferably in the form of a pipe joint having an axis substantially at right angles to the impeller axis and that the air inlet be substantially co-axial with the impeller axis. The pump housing may also be provided with means for attaching it to a mounting base for non-pipe support installations. In such arrangements the air communication means may be apertures through the wall, which can be above the pipe joint when the air pump assembly is supported on a pipe or on a base.
These arrangements of the air outlet have the advantage that return air impinges directly on the pump casing where it will preferentially condense thus reducing damage to the motor. Further any return water will accumulate in the pump housing before passing to the motor housing, thus reducing the occurrence of water damage to the motor.
Preferably the motor housing is relatively voluminous so as to provide significant air space around the motor which may absorb heat during start up. This will prolong the time taken to overheat the motor and increase the chance of purging the air supply pipes prior to damaging the motor. enabling